The invention relates to a method for winding a skein-shaped windable product onto a spool consisting of two spool halves which converge conically towards a middle radial plane with two flange discs at the outer ends, the spool being rotated about its central axis during the winding process, and the windable product being fed by a guide that moves along the length of the spool.
There are many prior methods for winding a skein-shaped windable product onto spools. One example is DE 38 44 964 C2, which contains further references to the state of the art, such as EP 29 971 A1 or EP 241 964 A2. Also worth mentioning in this context is EP 672 016 B2. This document describes a spool with a conical winding core and two flange discs at the ends. At the least, the flange disc on the side of the smaller diameter can be removed from the winding core.
When designing spools of this type, and also the related winding method, practical reasons necessitate consideration of certain requirements, especially with regard to unwinding the windable product at the processing site. For example, the spools may be disposed in standing fashion during the unwinding process, in which case the windable product is unwound upwards. The spool does not rotate during this process. The windable product is first deflected through the top flange and fed to the region of the elongated central axis where it is connected to a guide device by means of which it is then unwound. The need to deflect the windable product through the top flange can cause heavy friction and may damage, or even break, the windable product. Care is therefore taken to ensure that the diameter of the upper portion of the winding core is as large as possible to minimise the deflection suffered by the windable product during unwinding. The rule is that the ratio of the flange diameter to the core diameter should not be greater than 2:1.
That is offset by the desire to achieve a high winding volume, which is facilitated by keeping the core diameter as small as possible.
Furthermore, it must be ensured that the process of unwinding the windable product can be interrupted without any risk of the windable product still on the core slipping downwards. This could, for example, happen with a winding core that tapers conically downwards, although on the other hand, this might be one way of meeting the requirement to ensure a portion with a large diameter at the upper end. The aforementioned EP 672 016 B2 therefore suggests a winding method which makes use of a standing winding core that tapers conically downwards, but wherein the windable product is deposited in inverted cone shape in layers built up from bottom to top.
This meets the two aforementioned requirements in that the upper end of the winding core has a large diameter, ensuring that the friction during the deflection of the windable product is acceptable, and, on the other hand, the windable product is prevented from slipping downwards if the unwinding process has to be interrupted. Spools of the type described also offer the possibility, once the flange on the side with the smaller diameter has been removed, of stacking the spools to save space whenever they are empty and have to be transported or stored. Spools of this type are associated with some disadvantages, however, resulting for example from the axial asymmetry, or from the fact that when made from plastic, tools of considerable size are required. Furthermore, two different parts are always required to make one spool, which naturally requires two injection moulding tools if the parts are made from plastic. One also has to have two different parts available for one spool. For these reasons, the preference is often for spools consisting of two spool halves or parts which converge from opposite directions towards the middle, upon which the present invention is based. Spools of this type can be separated along a central radial plane and the resultant spool parts are identical and can be stacked together.